Method and apparatus for temperature control of heater

ABSTRACT

A CVD device ( 100 ) includes a 142 process chamber ( 102 ), in the wall of which first to fourth cartridge heaters ( 146, 148, 150, 152 ) are buried. The heaters have resistance whose value increases with temperature. A heater controller ( 160 ) determines the heater resistance from the current and voltage values associated with each heater. The heater controller ( 160 ) corrects a reference resistance corresponding to a set temperature by using a correction value corresponding to the temperature detected by a temperature sensor ( 250 ), and multiplies the corrected reference resistance by the temperature distribution constant of each heater to determine the target resistance. The heater controller ( 160 ) properly controls the phase of the AC power supplied to each heater so that the heater resistance may follow the target resistance. The first to fourth cartridge heaters ( 146, 148, 150, 152 ) are thus controlled accurately.

TECHNICAL FIELD

The present invention relates to an apparatus and method forimplementing temperature control on a means for heating.

BACKGROUND ART

Various types of semiconductor manufacturing apparatuses having a heaterare used in the process of manufacturing a semiconductor device. Forinstance, heaters are provided at a process chamber wall, a stage onwhich a semiconductor wafer (hereafter referred to as a “wafer”) isplaced and the like in a thermal CVD (film forming) device. Thus, in thethermal CVD device, film formation processing is implemented afterheating the process chamber wall and the stage to a specific temperaturewith the heaters. In addition, temperature control of the heaters isimplemented by a temperature control apparatus. The temperature controlapparatus compares the set temperature and the temperature at a heaterdetected by a thermal (temperature) sensor. Then, the temperaturecontrol apparatus implements on/off control of the power supplied to theheater through switching so as to set the two temperatures roughly equalto each other through an adjustment of the quantity of heat generated bythe heater. In addition, an interlocking thermal sensor (hereafterreferred to as an “interlock sensor”) is connected to the temperaturecontrol apparatus. The temperature control apparatus stops power supplyto a heater if the temperature of the heater detected by the interlocksensor indicates a level equal to or higher than the temperature upperlimit set at the temperature control apparatus.

However, in the prior art described above, it is necessary to provide athermal sensor and an interlock sensor in correspondence to each heater.For this reason, if there are a plurality of heaters, the number ofindividual types of sensors and the wirings required to connect thesensors to the temperature control apparatus are bound to increase incorrespondence to the number of heaters. As a result, a problem arisesin the prior art in that a large initial cost must be incurred since agreat number of sensors must be provided.

In addition, there is another problem in the prior art technology inthat the maintainability of the apparatus is lowered due to the complexand time-consuming inspection and testing process that must be conductedon the sensors and the wirings.

In the prior art, the apparatus is bound to be large because of thelarge numbers of sensors and wirings. Consequently, there is a problemin that the technological requirement for miniaturizing devices such asthe CVD device provided in the clean room cannot be met.

Furthermore, the temperature at a heater cannot be directly detected inthe prior art. Thus, the heater temperature cannot be ascertainedaccurately, to lead to a problem of unstable heater temperature control.

In the prior art technology, even when heating a single member by usinga plurality of heaters, the temperatures at the individual heaters aresustained at levels roughly equal to one another regardless of thepositions at which the heaters are installed. As a result, mutualinterference occurs between the heat generated at a given heater and theheat generated at another heater, thereby presenting a problem in thatuniformity is not achieved with regard to the temperature of the member.

Moreover, the temperature of a heater is adjusted by supplying power ata specific level to the heater through on/off control implemented on thepower in the prior art. This results in a problem in that accuratetemperature control cannot be achieved since there is a great differencein the heater temperature when power is on and the heater temperaturewhen power is off and the heater temperature is not sustained at aconstant level.

The object of the present invention, which has been completed byaddressing the problems of the prior art discussed above, is to providea new and improved apparatus and a new and improved method forimplementing temperature control on a means for heating, that solve theproblems discussed above and other problems as well.

DISCLOSURE OF THE INVENTION

In order to achieve the object described above, in a first aspect ofthe, present invention, a temperature control apparatus that implementstemperature control on a means for heating which heats an object to beheated, comprising at least two means for heating each with theresistance thereof increasing as the temperature rises, at least onemeans for temperature detection that detects the temperature of theobject to be heated, a means for target resistance calculation thatcalculates a target resistance for each of the means for heating bycorrecting a reference resistance determined based upon the settemperature for the object to be heated with a correction value obtainedin correspondence to the temperature detected by the means fortemperature detection and multiplying the corrected reference resistanceby a temperature distribution constant that is determined in advance foreach means for heating to adjust the temperature distribution at theobject to be heated, a means for actual resistance calculation thatdetermines the actual resistance at each of the means for heating basedupon a feedback voltage value obtained based upon the voltage applied tothe means for heating and a feedback current value obtained based uponthe current flowing through the means for heating and, a means for powercontrol that controls the power applied to each means for heating sothat the actual resistance at the means for heating conforms to thetarget resistance, is provided.

According to the present invention, means for heating each having aresistance that increases in proportion to an increase in temperatureare utilized. As a result, the temperature at each means for heating canbe ascertained based upon the actual resistance determined incorrespondence to the feedback voltage value and the feedback currentvalue obtained from the means for heating. Thus, the need for providinga means for temperature detection that detects the temperature at ameans for heating and a means for connection such as a wiring thatconnects the means for temperature detection to the temperature controldevice for each means for heating is eliminated. Consequently, even whenheating the object to be heated by utilizing a plurality of means forheating, the initial cost can be minimized and, at the same time, themaintenance work is facilitated. Furthermore, since the temperature ateach means for heating can be directly detected, accurate and stabletemperature control can be implemented on the means for heating.

In addition, according to the present invention, the referenceresistance used as the reference value when implementing control on eachmeans for heating is corrected by using a correction value obtained incorrespondence to the temperature detected by the means for temperaturedetection. By adopting such a structure, it becomes possible to controleach means for heating based upon the actual temperature of the objectto be heated as well as based upon the set temperature, is provided. Asa result, even more accurate temperature control on the individual meansfor heating is achieved to set the temperature of the object to beheated even closer to the set temperature. Furthermore, according to thepresent invention, the target resistance is obtained by multiplying thecorrected reference resistance by a temperature distribution constantthat is provided to adjust the temperature distribution of the object tobe heated. When such a target resistance is adopted, the temperatures ofthe means for heating can be adjusted in conformance to the temperaturelevels at the individual portions of the object to be heated. Thus, thetemperature of the object to be heated can be maintained in an even moreconsistent manner. Moreover, the ratio of the temperatures of theindividual means for heating can be adjusted so as to achieve uniformityin the temperature of the entire object to be heated in this structure.As a result, accurate temperature management is achieved for the objectto be heated. The actual resistance at each means for heating iscalculated by the means for actual resistance calculation. Consequently,the change in the value of each actual resistance can be ascertainedalmost concurrently while the change in the temperature at thecorresponding means for heating is detected. Thus, an improvement in theresponse of the means for heating is achieved.

It is desirable to employ a means for phase control that implementsphase control on the power applied to the individual means for heatingas the means for power control. In such a structure, by changing thephase of the AC power applied to the means for heating as appropriate,the temperatures at the means for heating can be adjusted. As a result,finer control on the means for heating is achieved compared to on/offpower control implemented through a means for interruption such as aswitch. Consequently, the temperature of the object to be heated isstabilized.

Through the means for phase control, the length of time over which poweris applied should be increased if the actual resistance is lower thanthe target resistance, the current length of power application should besustained if the actual resistance is essentially equal to the targetresistance and the length of time over which power is applied should bereduced if the actual resistance is higher than the target resistance,to achieve a prompt and reliable adjustment of the temperature of themeans for heating.

Alternatively, it is desirable to employ a means for zero cross controlthat implements zero cross control on the power applied to theindividual means for heating as the means for power control. In thisstructure in which power on/off is implemented when the voltage is atzero, noise occurs less readily in the power. As a result, the power issupplied to the means for heating in a stable manner, to furtherstabilize the temperature of the means for heating.

As a further alternative, the means for power control may be constitutedof a means for linear control that implements linear control on thepower applied to the means for heating. By adopting such a structure,the power can be controlled continuously. As a result, better control isachieved on each of the means for heating. Furthermore, since noise doesnot occur readily in the power, stable temperature control is achieved.

It is desirable to connect a means for power supply suspension thatsuspends the power supply to a means for heating if the actualresistance becomes higher than a resistance upper limit or becomes lowerthan a resistance lower limit. By adopting such a structure, it becomespossible to detect an error at a means for heating or the like basedupon the individual resistance values. Thus, the need for providing ameans for temperature detection that detects an abnormality in thetemperature and a wiring for connecting the means for temperaturedetection to the temperature control apparatus is eliminated. As aresult, a further reduction in the initial cost and a furtherimprovement in the maintainability are achieved.

The present invention achieves particularly outstanding advantages whenadopted in an application in which the object to be heated is a memberconstituting a semiconductor manufacturing apparatus or the like. In theprocess for manufacturing a semiconductor device, more accuratetemperature control must be achieved in order to supportultra-miniaturization and ultra-high integration of the semiconductordevice. Thus, by adopting the present invention in the temperaturecontrol of the member that needs to be heated, a higher degree ofaccuracy in temperature control is achieved. In addition, asemiconductor manufacturing apparatus or the like is often installed ina clean room. Accordingly, by employing the means for heating and thetemperature control apparatus in a semiconductor manufacturing apparatusand the like, miniaturization of the apparatus can be achieved since thenumbers of various means for temperature detection and the numbers ofthe means for connection are reduced. As a result, the space inside theclean room can be utilized efficiently or the size of the clean roomitself can be reduced. It is to be noted that the semiconductormanufacturing apparatus and the like in this context includes all thedevices used during the semiconductor manufacturing process such asvarious devices connected to the semiconductor manufacturing apparatusas well as the semiconductor manufacturing apparatus itself.

In a second aspect of the present invention, a temperature controlapparatus that implements temperature control on a means for heatingwhich heats an object to be heated, comprising at least two means forheating each with the resistance thereof increasing as the temperaturerises, at least one means for temperature detection that detects thetemperature of the object to be heated, a means for target voltagecalculation that calculates a target voltage for each of the means forheating by correcting a reference voltage determined based upon the settemperature for the object to be heated with a correction value obtainedin correspondence to the temperature detected by the means fortemperature detection and multiplying the corrected reference resistanceby a temperature distribution constant that is determined in advance foreach means for heating to adjust the temperature distribution at theobject to be heated, a means for voltage detection that detects theactual voltage applied to each of the means for heating and, a means forpower control that controls the power applied to each means for heatingso that the actual voltage at the means for heating conforms to thetarget voltage, is provided.

According to the present invention, each means for heating is controlledbased upon the target voltage value and the actual voltage.

The actual voltage can be obtained by detecting the voltage applied tothe means for heating without having to perform any arithmeticoperation. As a result, it is not necessary to provide a means foractual voltage calculation or to implement an arithmetic operation stepto calculate the actual voltage, thereby achieving simplification of theapparatus configuration and also simplification of the control process.

As in the first aspect of the invention, it is desirable to employ ameans for phase control that implements phase control on the powerapplied to the individual means for heating as the means for powercontrol. As in the first aspect of the invention, through the means forphase control, the length of time over which power is applied should beincreased if the actual voltage is lower than the target voltage, thecurrent length of power application should be sustained if the actualvoltage is essentially equal to the target resistance and the length oftime over which power is applied should be reduced if the actual voltageis higher than the target voltage.

As a desirable alternative, the means for power control may beconstituted of a means for zero cross control that implements zero crosscontrol on the power applied to each means for heating or a means forlinear control that implements linear control on the power applied toeach means for heating, as explained in reference to the first aspect ofthe invention.

As in the first aspect of the invention, it is desirable to connect ameans for power supply suspension that suspends the power supply to ameans for heating if the actual voltage becomes higher than the voltageupper limit or becomes lower than the voltage lower limit.

In addition, it is desirable to adopt the present invention in anapplication in which the object to be heated is a member constituting asemiconductor manufacturing apparatus and the like, as explained inreference to the first aspect of the invention.

In a third aspect of the present invention, a temperature control methodto be implemented on a means for heating that heats an object to beheated comprising a step in which a reference resistance determinedbased upon the set temperature for the object to be heated is correctedby using a correction value obtained in correspondence to thetemperature at the object to be heated detected by, at least, one meansfor temperature detection, a step in which the corrected referenceresistance is multiplied by a temperature distribution constant used toadjust the temperature distribution of the object to be heated, which isdetermined in advance for each of at least two means for heating eachwith a resistance that increases in correspondence to a temperatureincrease, to obtain a target resistance for each of the means forheating, a step in which the actual resistance at each of the means forheating is ascertained based upon a feedback voltage which correspondsto the voltage applied to each means for heating and a feedback currentvalue which corresponds to the current flowing through the means forheating and a step in which the power applied to each of the means forheating is controlled so that the actual resistance at the means forheating conforms to the target resistance, is provided.

In this method, the resistance at each means for heating increases asthe temperature of the means for heating increases. As a result, as inthe first aspect of the invention, temperature control on each means forheating is implemented based upon the corresponding actual resistancedetermined in conformance to the feedback voltage and the feedbackcurrent at the means for heating. Consequently, accurate temperaturemanagement is achieved for each means for heating. In addition,according to the present invention, the reference resistance iscorrected based upon the detected temperature, as in the inventiondisclosed in claim 1. Thus, more accurate temperature control isachieved. Furthermore, the target resistance is obtained by multiplyingthe corrected reference resistance by a temperature distributionconstant. Thus, even when heating the object to be heated with aplurality of means for heating, a consistent temperature distribution isachieved at the object to be heated in conformance to the current stateof the object to be heated, as in the invention disclosed in claim 1.

It is desirable that in the step for power control, phase control isimplemented on the power applied to each means for heating. By adoptingsuch a method, the temperatures of the means for heating are adjustedthrough phase control as explained in reference to the previous aspectsof the invention. As a result, the temperatures at the means for heatingcan be set with a high degree of accuracy.

Furthermore, it is desirable that the step in which phase control isimplemented on the power include a step in which the length of time overwhich power is applied is increased if the actual resistance is smallerthan the target resistance, a step in which the current length of powerapplication is sustained if the actual resistance is essentially equalto the target resistance and a step in which the length of time overwhich power is applied is reduced if the actual resistance is higherthan the target resistance. Through this method, the object to be heatedcan be set at a specific temperature with a high degree of reliability,as in the first aspect of the invention.

Alternatively, in the step for power control, zero cross control may beimplemented on the power applied to each means for heating.

By adopting this method, it is ensured that noise is less likely tooccur in the power applied to the means for heating, as in the previousaspect of the invention. As a result, power at a specific level issupplied in a stable manner.

As a desirable alternative, linear control may be implemented on thepower supplied to each means for heating in the step for power control.Through such a method, the power can be controlled continuously, as inthe previous aspects of the invention. As a result, better control isachieved.

Moreover, it is desirable to include a step in which the power supply toa means for heating is suspended if the actual resistance becomes higherthan the resistance upper limit or the actual resistance becomes lowerthan the resistance lower limit. By adopting this method, an error atthe means for heating can be detected based upon the actual resistancewithout having to provide a means for temperature detection that detectsa temperature abnormality at the means for heating, as explained earlierin reference to the first aspect of invention. Thus, damage to theobject to be heated and the like can be prevented.

Also, it is desirable that the object to be heated is a memberconstituting a semiconductor manufacturing apparatus and the like. Insuch a case, the temperature control on the semiconductor manufacturingapparatus and the like can be implemented in an ideal state, as in theprevious aspects of the invention.

In a fourth aspect of the present invention, a temperature controlmethod to be implemented on a means for heating that heats an object tobe heated comprising a step in which a reference voltage determinedbased upon the set temperature for the object to be heated is correctedby using a correction value obtained in correspondence to thetemperature of the object to be heated detected by, at least, one meansfor temperature detection, a step in which the corrected referencevoltage is multiplied by a temperature distribution constant used toadjust the temperature distribution of the object to be heated, which isdetermined in advance for each of at least two means for heating eachwith a resistance that increases in correspondence to a temperatureincrease to obtain a target voltage for each of the means for heating, astep in which the actual voltage applied to each of the means forheating is detected and a step in which the power applied to each meansfor heating is controlled so that the actual voltage at the means forheating conforms to the target voltage, is provided.

According to the present invention, each means for heating is controlledby using the corresponding actual voltage detected at the means forheating, as in the second aspect of the invention. Thus, it is notnecessary to provide a means for actual voltage calculation or toimplement an arithmetic operation step to calculate the actual voltage,to achieve simplification in the apparatus structure and simplificationin the control process.

As in the preceding aspects of the invention, it is desirable that inthe step for power control, phase control is implemented on the powerapplied to each means for heating. As in the preceding aspects of theinvention, it is desirable that the step in which phase control isimplemented on the power include a step in which the length of time overwhich power is applied is increased if the actual voltage is lower thanthe target voltage, a step in which the current length of powerapplication time is sustained if the actual voltage is essentially equalto the target voltage and a step in which the length of time over whichpower is applied is reduced if the actual voltage is higher than thetarget voltage.

As an alternative, in the power control step, zero cross control may beimplemented on the power applied to each means for heating or linearcontrol may be implemented on the power applied to each means forheating, as in the preceding aspect of the invention.

As in the preceding aspects of the invention, it is desirable to includea step in which power supply to a means for heating is suspended if theactual voltage becomes higher than the voltage upper limit or the actualvoltage becomes lower than the voltage lower limit.

As in the preceding aspects of the invention, it is desirable that theobject to be heated is a member constituting a semiconductormanufacturing apparatus and the like.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a sectional view schematically illustrating a CVD device whichmay adopt the present invention;

FIG. 2 is a perspective schematically illustrating the positions ofcartridge heaters provided in the CVD device shown in FIG. 1;

FIG. 3 is a perspective schematically illustrating the structure of acartridge heater provided in the CVD device shown in FIG. 1;

FIG. 4 schematically illustrates the characteristics achieved by theheating elements of various heaters provided at the CVD device shown inFIG. 1, and at a member connected to the CVD device;

FIG. 5 is a schematic block diagram of the heater controller shown inFIG. 1;

FIG. 6 is a schematic diagram illustrating the structure of a heatercontrol device shown in FIG. 5;

FIG. 7 schematically illustrates the phase control implemented by thephase control unit shown in FIG. 6;

FIG. 8 is a schematic block diagram of the arithmetic unit shown in FIG.6;

FIG. 9 schematically illustrates a structure that may be adopted in thearithmetic unit in another embodiment of the present invention;

FIG. 10 schematically illustrates a control structure that may beadopted in the mantle heater control in another embodiment of thepresent invention;

FIG. 11 schematically illustrates a heater controller achieved inanother embodiment of the present invention;

FIG. 12 schematically illustrates the control structure adopted in theheater controller shown in the FIG. 11;

FIG. 13 schematically illustrates zero cross control implemented inanother embodiment of the present invention; and

FIG. 14 schematically illustrates linear control implemented in anotherembodiment of the present invention.

BEST MODE FOR CARRYING OUT THE INVENTION

The following is an explanation of preferred embodiments of theapparatus and the method for implementing temperature control on a meansfor heating adopted in a heater controller employed in conjunction withheaters provided in a thermal CVD device. It is to be noted that thesame reference numbers are assigned to components having functions andstructural features essentially identical to one another in theindividual embodiments, to preclude the necessity for the repeatedexplanation thereof.

First Embodiment

This embodiment is characterized in that temperature control on aplurality of heaters is implemented based upon the resistances at theindividual heaters. The following is a detailed explanation of atemperature control apparatus and a temperature control method that areemployed to implement this temperature control.

(1) Structure of CVD Device

First, in reference to FIGS. 1 and 2, the structure of a CVD device 100,in which the present invention may be adopted is explained. A processchamber 102 in the CVD device 100 shown in FIG. 1 is formed within anairtight and conductive process container 104. In addition, the processcontainer 104 is covered with a heat insulating material 103. In thewall of the process chamber 102, first˜fourth cartridge heaters 146,148, 150 and 152 are mounted, as shown in FIGS. 1 and 2. Thefirst˜fourth cartridge heaters 146, 148, 150 and 152 are structuredessentially identical to one another and are each connected to a heatercontroller 160. In addition, at the outer wall surface of the processchamber 102, a temperature sensor 250 is provided. The temperaturesensor 250 is connected to a temperature control device 164 constitutingthe heater controller 160, which is to be detailed later. Thetemperature sensor 250 is installed at a position at which it can detectthe temperature at the inner wall surface of the process chamber 102with a high degree of sensitivity and the temperature of the memberchanges greatly, e.g., at the outer wall surface at the bottom of theprocess chamber 102.

As shown in FIG. 1, a stage 106 and a gas outlet member 108 are providedfacing opposite each other inside the process chamber 102. The stage 106is structured so that a wafer W can be placed on it. In addition, thestage 106 is internally provided with a resistance heater 112. A heatercontroller 110 is connected to the resistance heater 112.

Numerous gas outlet holes 108 a are formed at the gas outlet member 108.For this reason, the gas outlet member 108 assumes a so-calledshowerhead structure. The gas outlet holes 108 a communicate between agas supply pipe 120 and the process chamber 102. A branch pipe 128 and abranch pipe 136 are connected to the gas supply pipe 120. A gas supplysource 126 is connected to the branch pipe 128 via a flow-regulatingvalve 122 and a switching valve 124. The branch pipe 136 is connectedwith a gas supply source 134 via a flow-regulating valve 130 and aswitching valve 132. The gas supply source 126 is enclosed by a mantleheater (silicon rubber heater) 140. The mantle heater 140 is connectedto a heater controller 138. Furthermore, the branch pipe 128 and the gassupply pipe 120 are covered by a mantle heater 144. The mantle heater144 is connected to a heater controller 142. The mantle heaters 140 and144 are covered with a heat insulating material (not shown).

A vacuum pump 252 is connected to the process chamber 102 via anevacuating pipe 145. In addition, an evacuation-quantity regulatingvalve 254, a switching valve 256 and a trap 258 are mounted at theevacuating pipe 145. The trap 258 is structured so that it is capable ofliquefying a liquefiable gas evacuated from the process chamber 102 andcollecting the liquefied gas. Furthermore, the evacuating pipe 145 isenclosed by a mantle heater 260. The mantle heater 260 is connected witha heater controller 262. The mantle heater 260 is covered with a heatinsulating material (not shown).

Next, in reference to FIG. 1, film formation processing performed at theCVD device 100 is explained. First, the heater controllers 110, 138,142, 262 and 160 implement control on the corresponding resistanceheater 112, mantle heaters 140, 144 and 260 and first˜fourth cartridgeheaters 146, 148, 150 and 152 as appropriate. Through such control, thestage 106 is heated to a temperature within a range of, for instance,400° C.˜600° C. In addition, the wall of the process chamber 102 isheated to, for instance, 150° C. The gas supply source 126 is heated to,for instance, 90° C. and the branch pipe 128 and the evacuating pipe 145are heated to, for instance, 150° C. As a result, a liquid or solid rawmaterial stored in the gas supply source 126, e.g., TiCl₄ (titaniumtetra-chloride) which is in a liquid state at normal temperature,becomes gasified. In addition, it becomes possible to supply TiCl₄ intothe process chamber 102 while TiCl₄ remains in a gasified state via thegas supply pipe 128 and the like. The gas evacuated from the processchamber 102 travels through the evacuating pipe 145 without becomingliquefied and is induced into the trap 258.

Next, the wafer W is placed on the stage 106. In addition, gasifiedTiCl₄ and NH₃ (ammonia) are induced into the process chamber 102 fromthe gas supply sources 126 and 134. The gas (atmosphere) within theprocess chamber 102 is evacuated by the vacuum pump 252. By inducing andevacuating the processing gas in this manner, the atmosphere within theprocess chamber 102 is set at a specific pressure level. As a result, aTiN (titanium nitride) film is formed on the wafer W with the processinggas induced into the process chamber 102.

(2) Structures of Heaters

Next, the structures of the individual heaters provided in the CVDdevice 100 are explained. It is to be noted that the structures assumedby the heating elements at the resistance heater 112, the mantle heaters140, 144 and 260 and the first˜fourth cartridge heaters 146, 148, 150and 152 are essentially identical to one another. Accordingly, anexplanation is given below on the structure of the first cartridgeheater 146 as a typical example.

The first cartridge heater 146 shown in FIG. 3 comprises a cylindricalbody 154 which may be constituted of, for instance, stainless steel, aheating wire 156 and a filler material 158 which may be constituted of,for instance, MgO (magnesium oxide). The heating wire 156 is set at anapproximate center inside the cylindrical body 154. In addition, thefiller material 158 is provided to fill the space between the heatingwire 156 and the inner wall surface of the cylindrical body 154.

The heating wire 156 is constituted of an alloy containing Fe (iron) andmore preferably an alloy constituted of Fe and Ni (nickel) (hereafterreferred to as an “Fe-Ni alloy”). The Fe-Ni alloy demonstratescharacteristics whereby the resistance increases greatly in proportionto a rise in the temperature, compared to an alloy (Nichrome)constituted of Ni and Cr (chrome) often utilized to constitute theheating elements of heaters in the prior art, and W (tungsten), Pt(platinum) and Ta (tantalum) in FIG. 4. Thus, the resistance of theheating wire 156 constituted of this material increases incorrespondence to a rise in the temperature resulting from AC powerapplication, as explained later. If, on the other hand, the AC powerapplication is suspended and the temperature becomes lowered, theresistance of the heating wire 156, too, becomes reduced.

Thus, the temperature of the first cartridge heater 146 can be detectedbased upon the resistance of the heating wire 156 itself. As a result,the temperature can be detected with a high degree of accuracy. Inaddition, by adopting this structure, the number of temperature sensorsand the number of wirings and the like connected to the sensors can bereduced. Consequently, the maintenance work is facilitated and initialcost can be reduced and the CVD device 100 can be minimized. It is to benoted that heating elements constituted of the Fe-Ni alloy are also usedin the second˜fourth cartridge heaters 148, 150 and 152, the resistanceheater 112 and the mantle heaters 140, 144 and 260 as well. Effects andadvantages identical to those achieved in the first cartridge heater 146are also achieved in the second˜fourth cartridge heaters 148, 150 and152, the resistance heater 112 and the mantle heaters 140, 144 and 260,as a result. Furthermore, the heating element may be also adopted in asheathed heater.

(3) Structures of Heater Controllers

(a) Overall Structures of Heater Controllers

Next, the structures of the heater controllers provided in the CVDdevice 100 are explained. Since the heater controllers 110, 138, 142,160 and 262 are structured identically to one another, an explanation isgiven below on the heater controller 160 as a typical example.

The heater controller 160 comprises the temperature control device 164and first˜fourth heater control devices 166, 168, 170 and 172, asillustrated in FIG. 5. The first˜fourth heater control devices 166, 168,170 and 172, which are structured identically to one another, are eachconnected to the temperature control device 164. In addition, thefirst˜fourth heater control devices 166, 168, 170 and 172 arerespectively connected with the first˜fourth cartridge heaters 146, 148,150 and 152. The temperature sensor 250 described earlier is connectedto the temperature control device 164.

When the required temperature at the wall of the process chamber 102(hereafter referred to as the “set temperature”) is set, the temperaturecontrol device 164 calculates a reference resistance in correspondenceto the set temperature. The set temperature should be a temperature at alevel at which no deposition adheres to the inner wall surface of theprocess chamber 102 during the film formation processing, e.g., 150° C.In addition, the reference of resistance is a value (a constant value)which is determined based upon the relationship between the temperatureand the resistance at the heating wire 156 shown in FIG. 4 explainedearlier. Consequently, when the temperatures of the first˜fourthcartridge heaters 146, 148, 150 and 152 (the temperature of the heatingwire 156) are set at 150° C. which is equal to the set temperature, forinstance, the reference resistance is approximately 90.29Ω. However, infact, there are inconsistencies among individual cartridge heaterproducts. For this reason, the reference resistance is determined foreach cartridge heater in actual application.

In addition, the temperature control device 164 obtains a correctionvalue as necessary based upon the temperature at the wall of the processchamber 102 detected by the temperature sensor 250. The correction valueis used to correct as necessary a reference resistance (a constantvalue) so as to set the temperature at the wall of the process chamber102 equal to the set temperature at all times based upon the differencebetween the set temperature and the temperature at the wall of theprocess chamber 102 during the control operation. If there is adifference between the set temperature and the temperature at the wallof the process chamber 102, the temperature control device 164 correctsthe reference resistance by using the correction value to obtain acorrected reference resistance. Accordingly, if there is a differencebetween the set temperature and the temperature at the wall of theprocess chamber 102, the corrected reference resistance changes incorrespondence to the temperature difference. In addition, if thetemperature at the wall of the process chamber 102 is equal to the settemperature, the corrected reference resistance is equal to thereference resistance. It is to be noted that in this specification, thereference resistance used to obtain target resistances R_(s1), R_(s2),R_(s3) and R_(s4) to be detailed later is referred to as a correctedreference resistance even when there is no difference between the settemperature and the temperature at the wall of the process chamber 102and thus, the reference resistance is not corrected. By assuming thestructure described above, the temperature control on the first˜fourthcartridge heaters 146, 148, 150 and 152 can be implemented with an evenhigher degree of accuracy.

The temperature control device 164 also calculates the targetresistances R_(s1), R_(s2), R_(s3) and R_(s4) by multiplying thecorrected reference resistances by temperature distribution constantsK₁, K_(s2), K₃ and K₄ respectively. The temperature distributionconstants K₁, K_(s2), K₃ and K₄ are used to determine the temperaturedistributions at positions (installation locations) at which heat isapplied by the first˜fourth cartridge heaters 146, 148, 150 and 152respectively so as to adjust the temperature over the entire inner wallsurface of the process chamber 102 consistently at the set temperaturein the embodiment. In addition, the temperature distribution constantsK₁, K_(s2), K₃ and K₄ are also used to correct any errors in thequantities of heat generated by the first˜fourth cartridge heaters 146,148, 150 and 152. For these purposes, the temperature distributionconstants K₁, K_(s2), K₃ and K₄ are individually determined in advancein correspondence to the first˜fourth cartridge heaters 146, 148, 150and 152 respectively.

Now, a method through which the temperature distribution constants K₁,K₂, K₃ and K₄ are obtained is explained. First, prior to the actualprocessing, a temperature sensor is set at each of the positions atwhich heat is applied by the first˜fourth cartridge heaters 146, 148,150 and 152. The individual temperature sensors are structuredessentially identical to the temperature sensor 250. The temperaturesensors are mounted at positions at which they can detect changes in thetemperatures of the first˜fourth cartridge heaters 146, 148, 150 and 152with a high degree of sensitivity. After the temperature sensors aremounted, control is implemented by the first˜fourth heater controldevices 166, 168, 170 and 172 on the corresponding first˜fourthcartridge heaters 146, 148, 150 and 152 to raise the temperatures of thefirst˜fourth cartridge heaters to specific levels, e.g., thetemperatures of all the cartridge heaters are raised to a single settemperature. During this process, the first˜fourth heater controldevices 166, 168, 170 and 172 implement control independently of oneanother, based upon the temperatures detected by the correspondingtemperature sensors. Then, after the temperatures of the first˜fourthcartridge heaters 146, 148, 150 and 152 all become stabilized at the settemperature, the actual resistances at the first˜fourth cartridgeheaters 146, 148, 150 and 152 at this temperature level are recorded.

Next, the temperature distribution constants K₁, K_(s2), K₃ and K₄ arecalculated based upon the individual actual resistances recorded above.First, 1 is set for the temperature distribution constant correspondingto one of the temperature sensors, e.g., for the temperaturedistribution constant K₁ at the detection position of the temperaturesensor 250 manifesting the largest change in temperature. In addition,based upon the actual resistance at the first cartridge heater 146corresponding to the temperature sensor 250 and the individual actualresistances at the second˜fourth cartridge heaters 148, 150 and 152corresponding to the temperature sensors other than the temperaturesensor 250, a proportional operation is performed to calculate theresistances. As a result, coefficients calculated through theproportional operation are set as the temperature distribution constantsK₁, K_(s2), K₃ and K₄ corresponding to the first˜fourth cartridgeheaters 146, 148, 150 and 152 respectively.

A further explanation is given on the temperature control device 164.The temperature control device 164 outputs signals based upon the targetresistances R_(s1), R_(s2), R_(s3) and R_(s4) to the correspondingfirst˜fourth heater control devices 166, 168, 170 and 172 respectively.The target resistances R_(s1), R_(s2), R_(s3) and R_(s4) increase as thevalues of the temperature distribution constants K₁, K₂, K₃ and K₄increase. In addition, the temperatures of the heating elements (156) ofthe first˜fourth cartridge heaters 146, 148, 150 and 152 rise as theresistances increase, as shown in FIG. 4. Accordingly, the temperaturesof the first˜fourth cartridge heaters 146, 148, 150 and 152 becomehigher as the target resistances R_(s1), R_(s2), R_(s3) and R_(s4)increase. If, on the other hand, the values of the temperaturedistribution constants K₁, K₂, K₃ and K₄ are smaller, the targetresistances R_(s1), R_(s2), R_(s3) and R_(s4) also become lower. Also,as shown in FIG. 4, the temperatures of the heating elements (156) ofthe first˜fourth cartridge heaters 146, 148, 150 and 152 become lower asthe resistances decrease. As a result, the temperatures of thefirst˜fourth cartridge heaters 146, 148, 150 and 152 become lower as thetarget resistances R_(s1), R_(s2), R_(s3) and R_(s4) are reduced. Inaddition, the target resistances R_(s1), R_(s2), R_(s3) and R_(s4)change in response to changes in the values of the corrected referenceresistances resulting from the correction explained earlier.

In the structure described above, the temperatures of the first˜fourthcartridge heaters 146, 148, 150 and 152 installed at varying positionsare set individually and independently of one another. Thus, even whenthe wall of the process chamber 102, i.e., the inner wall surface of theprocess chamber 102, is heated by using a plurality of heaters, i.e.,the first˜fourth cartridge heaters 146, 148, 150 and 152, uniformity inthe temperature is assured over the entire inner wall surface of theprocess chamber 102.

The first˜fourth heater control devices 166, 168, 170 and 172 controlthe power, e.g., the phase of AC power, supplied to the first˜fourthcartridge heaters 146, 148, 150 and 152 based upon the correspondingtarget resistances R_(s1), R_(s2), R_(s3) and R_(s4) and heaterresistances R_(s1), R_(s2), R_(s3) and R_(s4) which are to be explainedlater. In addition, the first˜fourth heater control devices 166, 168,170 and 172 keep the temperature of the inner wall of the processchamber 102 at a specific level by controlling the quantities of heatgenerated by the first˜fourth cartridge heaters 146, 148, 150 and 152 .

(b) Structures of Heater Control Devices

Next, the structures assumed by the first˜fourth heater control devices166, 168, 170 and 172 are explained by focusing on the first heatercontrol device 166 shown in FIG. 6 as an example. First, the heatercontrol device 166, which is constituted of a heater control unit 174and an interlock control unit 175, controls the phase of the AC powersupply to the first cartridge heater 146. The heater control unit 174 isconstituted of a voltage sensor 176, a current sensor 178, low passfilters 180 and 182, an arithmetic unit 184, and amplifier 186 and aphase control unit 188. The phase control unit 188 is constituted of atriac control unit 190 and a triac (AC switch) 192 connected to thetriac control unit 190.

The voltage sensor 176 measures a feedback voltage value V_(R) which isdetermined based upon the voltage applied to the first cartridge heater146. A signal corresponding to the feedback voltage value V_(R) isoutput to the arithmetic unit 184 via the low pass filter 180. Thecurrent sensor 178, on the other hand, measures a feedback current valueI_(R) which is determined based upon the current flowing through thefirst cartridge heater 146. A signal corresponding to the feedbackcurrent value I_(R) is output to the arithmetic unit 184 via the lowpass filter 182. The arithmetic unit 184 calculates a heater resistanceR_(R1) representing the actual resistance at the first cartridge heater146 based upon the feedback voltage value V_(R) and the feedback currentvalue I_(R) as is to be detailed later. In addition, the arithmetic unit184 outputs a signal corresponding to the heater resistance R_(R1) tothe triac control unit 190 via the amplifier 186. The arithmetic unit184 also outputs a signal corresponding to the heater resistance R_(R1)to comparators 196, 198 and 200 to be detailed later, which constitutesthe interlock control unit 175. It is to be noted that the structure ofthe arithmetic unit 184 is to be explained later. A signal correspondingto the target resistance R_(s1) output from the temperature controldevice 164 is input to the amplifier 186. Thus, the signal correspondingto the target resistance R_(s1) is provided to the triac control unit190 via the amplifier 186.

One end of an AC source 194 is connected to the triac control unit 190.In addition, an RS latch 214 constituting the interlock control unit 175is connected to the triac control unit 190. The other end of the ACsource 194 and the output end of the triac 192 are connected to theindividual input ends of the first cartridge heater 146.

In this structure, the triac control unit 190 controls the phase of theAC power that is output from the triac 192 to the first cartridge heater146 so as to equalize the heater resistance R_(R1) to the targetresistance R_(s1) with the heater resistance R_(R1) conforming to thetarget resistance R_(s1). In other words, the triac control unit 190implements the control described above so that the temperature of thefirst cartridge heater 146 is set essentially equal to the temperaturedetermined by the temperature control device 164 (hereafter referred toas a “target temperature”).

To explain in further detail, the triac control unit 190 implementscontrol on the triac 192 to increase the length of time over which theAC power is applied at ½ cycles and thus increase the quantity of heatthat is generated if the heater resistance R_(R1) is lower than thetarget resistance R_(s1), and the temperature of the first cartridgeheater 146 is lower than the target temperature, as shown in FIG. 7(a).In addition, if the heater resistance R_(R1) and the target resistanceR_(s1) are roughly equal to each other and the temperature of the firstcartridge heater 146 is essentially equal to the target temperature, itimplements control on the triac 192 to sustain the current length oftime over which the AC power is applied at ½ cycles to sustain thequantity of heat that is generated at a constant level, as shown in FIG.7(b). If the heater resistance R_(R1) is higher than the targetresistance R_(s1) and that temperature of the first cartridge heater 146is higher than the target temperature, it implements control on thetriac 192 so as to reduce the length of time over which the AC power isapplied at ½ cycles to reduce the quantity of heat generated, as shownin FIG. 7(c).

As described above, the temperature of the first cartridge heater 146 isadjusted by implementing ½ cycle phase control on the AC power appliedto the first cartridge heater 146. As a result, a temperature deviationoccurs less readily than in a structure in which the temperature isadjusted through on/off control on the power. Thus, the temperature ofthe first cartridge heater 146 can be sustained evenly.

The interlock control unit 175 is constituted of the comparators 196,198 and 200, low pass filters 202, 204 and 206, a NOR gate 208, an ANDgate 210, an invertor circuit 212 and the RS latch 214.

The comparator 196 outputs an open circuit signal via the low passfilter 202 if the heater resistance R_(R1) is higher than a referencevalue used to judge the open (disconnect) state of the circuitconstituting the heater control unit 174. Part of the open circuitsignal is provided to the RS latch 214 via the invertor circuit 212, theAND gate 210 and the NOR gate 208 and another part of the open circuitsignal is provided to a circuit other than the first heater controldevice 166.

The comparator 198 outputs an overheat signal via the low pass filter204 if the heater resistance R_(r1) is higher than a reference valueused to judge whether or not the first cartridge heater 146 is in anoverheated state. The reference value represents, for instance, theresistance of the heating wire 156 when the temperature at the innerwall surface of the process chamber 102 has reached 190° C. or thesurface of the heat insulating material 103 has reached 50° C. Inaddition, part of the overheat signal is provided to the RS latch 214via the NOR gate 208 and another part of the overheat signal is providedto a circuit other than the first heater control device 166 via the ANDgate 210.

The comparator 200 outputs a short circuit signal via the low passfilter 206 if the heater resistance R_(R1) is lower than a referencevalue used to judge whether not the circuit constituting the heatercontrol unit 174 is in a shorted state. Part of the short circuit signalis provided to the RS latch 214 via the NOR gate 208 and another part ofthe short circuit signal is provided to a circuit other than the firstheater control device 166.

In addition, the RS latch 214 is provided with an enable signal and areset signal which is input via the NOR gate 208, as well as the signalsexplained above. When a specific signal is input, the RS latch 214outputs an interlock signal to the triac control unit 190. The specificsignal is constituted of at least one of; the open circuit signal, theoverheat signal and the short circuit signal. When the interlock signalis input, the triac control unit 190 suspends the supply of the AC powerfrom the triac 192 to the first cartridge heater 146. In addition, theoutput of the interlock signal is stopped by inputting the reset signalto the RS latch 214. By inputting the enable signal to the RS latch 214,the interlock signal is output to the triac control unit 190 regardlessof whether or not the open circuit signal, the overheat signal or theshort circuit signal is input.

By adopting the structure described above, it is possible to detect anyerror such as the first cartridge heater 146 becoming overheated to atemperature equal to or higher than a specific upper limit or a failureoccurring at the heater control unit 174, based upon the heaterresistance R_(r1) This eliminates the need for providing an interlocksensor such as a thermostat or the like at the CVD device 100. It is notnecessary to provide a wiring or the like to connect the sensor to theheater controller 160, either. As a result, a further reduction in thecost, a further improvement in the maintainability and furtherminiaturization of the apparatus are achieved. Moreover, errors such asthe first cartridge heater 146 becoming heated to an abnormally hightemperature can be detected directly. Thus, corrective measures can betaken quickly in response to an error to minimize damage to the device.

(c) Structure of Arithmetic Unit

Next, in reference to FIG. 8, the structure assumed by the arithmeticunit 184 is explained. The arithmetic unit 184 is constituted ofresistive elements 216, 218 and 220, amplifiers 222 and 224, atransistor 226 and a photo coupler 228. The photo coupler 228 isconstituted of an LED (light emitting diode) 230 and light-receivingelements (resistive elements) 232 and 234 which may be constituted of,for instance, CdS (cadmium sulfide).

The resistive element 216 achieving a resistance R₁ and thelight-receiving element 232 achieving a resistance R₂ are connected toone end (−) at the input end of the amplifier 222. The low pass filter182 shown in FIG. 6 is connected to the resistive element 216. The otherend (+) at the input end of the amplifier 222 is grounded. At the outputend of the amplifier 222, the base of the transistor 226 and thelight-receiving element 232 are connected. The emitter of the transistor226 is connected to the anode (a P-type semiconductor) of the LED 230via the resistive element 218 achieving a resistance R₃. The collectorof the transistor 226 is grounded. In addition, a grounded DC source 236is connected to the cathode (an N-type semiconductor) of the LED 230.

When a voltage V_(1IN) of a feedback current value I_(R) signal is inputto the resistive element 216 through the low pass filter 182, a currentI₁ flows to the resistive element 216. The voltage V_(1IN) is amplifiedat the amplifier 222 which then outputs a voltage V_(1OUT) . The voltageV_(1OUT) is then input to the resistive element 218 via the transistor226, causing a current 12 to flow to the resistive element 218.

The resistive element 220 and the light-receiving element 234 areconnected to one end (−) at the input end of the amplifier 224. The lowpass filter 180 shown in FIG. 6 is connected to the resistive element220. The other end (+) at the input end of the amplifier 224 isgrounded. At the output end of the amplifier 224, the light-receivingelement 234 and the amplifier 186 and the comparators 196, 198 and 200shown in FIG. 6 are connected.

Next, the process implemented by the arithmetic unit 184 to calculate aheater resistance R_(R) based upon the feedback voltage value V_(R) andthe feedback current value I_(R) is explained in reference to themathematical expressions presented below.

First, the resistance R₂ at the light-receiving element 232 is solved byusing the voltage V_(1OUT) output by the amplifier 222 to obtain thecurrent I₂ flowing through the resistive element 218 expressed as;

I ₂=(V _(1OUT)−(−V _(cc))−V _(be) −V _(LED))/R ₃  (1),

with −V_(cc) representing the voltage at the DC source 236, V_(be)representing the voltage between the base and the emitter of thetransistor 226 and VLED representing the voltage at the LED 230. Bysubstituting “V_(cc)−V_(be) −V_(LED)” in expression (1) with V_(CONST),expression (1) is rendered to;

I₂=(V_(1OUT) +V _(CONST))/R ₃  (2)

In addition, since the resistance R2 is in reverse proportion to thecurrent I₂;

1/R ₂ =K ₁ ·I ₂  (3)

is true, with K₁ representing the current amplification factor at theLED 230.

By incorporating expression (2) above in expression (3), 1/R₂ isre-expressed as;

1/R ₂ =K ₁(V _(1OUT) +V _(CONST))/R ₃  (4)

Expression (4) is modified to;

V _(1OUT)=(R ₃/(R ₂ K ₁))−V _(CONST)  (5)

The voltage V_(1IN) corresponding to the feedback current value I_(R) isexpressed as;

V _(1IN) =R ₁ I ₁

 =R ₁(V _(1OUT) /R ₂)

=(R ₁ /R ₂)((R ₃/(R ₂ K ₁))−V_(CONST)

=((R ₁ R ₃)/(R ₂ ² K ₁))−(R ₁ /R ₂)V _(CONST)  (6)

By conforming to conditions R₂ ² K₁ >>R₁ ·R₃, expression (6) above ismodified to;

V _(1IN)=−(R ₁ /R ₂)V _(CONST)  (7)

The voltage V_(2OUT) corresponding to the heater resistance R_(R1) isexpressed as;

V _(20UT)=−(R ₅ /R ₄)V _(2IN)  (8)

The light-receiving elements 232 and 234 mentioned earlier achieveelectrical characteristics that are essentially identical to each other.Thus, the resistance R₂ at the light receiving element 232 and theresistance R₅ at the light receiving element 234 can be regarded to beessentially equal to each other. Consequently, by incorporatingexpression (7) in expression (8), V_(2OUT) is expressed as;

V _(2OUT)=−(1/R ₄)(−(R ₁ /V _(1IN))V _(CONST))V _(2IN)

=(V _(2IN) /V _(1IN))(R ₁ /R ₄)V _(CONST)  (9)

Three conditions expressed as;

(R ₁ /R ₄)·V _(CONST)=constant (CONST)

V _(2IN) =k ₁ ·V _(R) and

V _(1IN) =k ₂ ·I _(R)

are imposed on expression (9). As a result, the voltage V_(2OUT) isexpressed as;

V _(2OUT) =k·(V _(R) /I _(R))=kR _(R1)

k₁ and k₂ each represent a specific constant. In addition, k=k₁/k₂ andR_(R1)=V_(R)/I_(R) are true with respect to k and R_(R). Thus, thevoltage V_(2OUT) output from the arithmetic unit 184 changes inproportion to the heater resistance R_(R1).

Through the arithmetic operation described above, the heater resistanceR_(R1) can be ascertained with ease by simply inputting the feedbackvoltage value V_(R) and the feedback current value I_(R) to thearithmetic unit 184. In addition, the photo coupler 228 is employed as aconstituent of the arithmetic unit 184. As a result, the heaterresistance can be obtained in a stable manner even when the feedbackcurrent value is small, thereby making it possible to produce thearithmetic unit 184 at a relatively low cost. In addition, the heaterresistance R_(R1) can be ascertained quickly through an arithmeticoperation by adopting this structure. Consequently, the first cartridgeheater 146, can be controlled with good response.

The first cartridge heater 146 is controlled as described above. Thesecond˜fourth cartridge heaters 148, 150 and 152 , too, are controlledin a manner similar to that with which the first cartridge heater 146 iscontrolled, to keep their temperatures at specific levels. In addition,by correcting the reference resistances at the other heaters, i.e., theresistance heater 112 and the mantle heaters 140, 144 and 260, basedupon the temperatures detected by the temperature sensors, as in thethird embodiment to be detailed later, control similar to thatimplemented on the first˜fourth cartridge heaters 146, 148, 150 and 152is achieved for the resistance heater 112 and the mantle heaters 140,144 and 260.

Second Embodiment

Next, the second embodiment of the present invention is explained. Theembodiment is characterized in that the heater resistance is calculatedby employing an arithmetic unit 300 adopting a simpler structure thanthe arithmetic unit 184 provided with the photo coupler 228. Namely, thearithmetic unit 300 comprises a multiplier 302 constituted of an analogintegrated circuit, resistive elements 304 and 306 and an amplifier 308,as shown in FIG. 9. The low pass filter 182 shown in FIG. 6 is connectedto one end at the input end of the multiplier 302. The output end of theamplifier 308 is connected to the other end at the input end of themultiplier 302. At one end (−) at the input end of the amplifier 308,the output end of the multiplier 302 and the low pass filter 180 shownin FIG. 6 are connected respectively via the resistive element 304 andthe resistive element 306. The other end (+) at the input end of theamplifier 308 is grounded. The output end of the amplifier 308 isconnected to the input end of the multiplier 302 and also to theamplifier 186 and the comparators 196, 198 and 200 shown in FIG. 6. Thelow pass filters 180 and 182 respectively output the voltage V_(2IN) anda voltage V_(1IN) as explained earlier. The multiplier 302 outputs avoltage V_(OUT). The amplifier 308 outputs the V_(2OUT) mentionedearlier. The resistive element 304 and the resistive element 306respectively achieve a resistance R₆ and a resistance R₇.

Next, the arithmetic operation performed by the arithmetic unit 300 tocalculate the heater resistance R_(R1) is explained in reference to themathematical expressions presented below. The voltage V_(OUT) output bythe multiplier 302 is expressed as;

V _(OUT) =V _(1IN) V _(2OUT)  (10)

The input end (−) of the amplifier 308 is an imaginary short. Thus,

(V _(OUT) /R ₆)+(V _(2IN) /R ₇)=0  (11)

is true. Expression (11) is incorporated in expression (10) to calculatethe voltage V_(2OUT), which is then expressed as;

V _(2OUT)=−(R ₆ /R ₇)(V _(2IN) /V _(1IN))  (12)

Assuming that R₆=R₇, the voltage V_(2OUT) is expressed as;

V _(2OUT)=−(V _(2IN) /V _(1IN))

As described above, the arithmetic unit 300 functions as a divider andthe voltage V_(2OUT) can be ascertained based upon the voltages V_(1IN)and V_(2IN). As a result, the heater resistance R_(R1) which changes inproportion to the voltage V_(2OUT) can be determined. Since otherstructural features are essentially identical to those assumed in theCVD device 100 explained earlier, their explanation is omitted.

By employing the arithmetic unit 300 structured as described above, thenumber of elements and the like constituting the arithmetic unit 300 canbe reduced. Consequently, the offset adjustment is simplified. Inaddition, the in uniformity in the characteristics of the individualelements can be reduced to achieve an improvement in arithmeticoperation accuracy. Furthermore, the circuit of the arithmetic unit 300can be achieved through a relatively simple structure. As a result, thearithmetic unit 300 can be miniaturized so that it can be installed in asmall space.

Third Embodiment

Next, the third embodiment of the present invention is explained. Theembodiment is characterized in that the temperatures of the mantleheaters 140, 144 and 260 are controlled based upon the actualresistances at the mantle heaters 140, 144 and 260 and the temperaturesdetected by the temperature sensors. It is to be noted that since thetemperatures of the mantle heaters 140, 144 and 260 are each controlledin a manner essentially identical to the manner with which thetemperatures of the other mantle heaters are controlled, an explanationis given on the temperature control implemented on the mantle heater 260as a typical example.

As already explained, the mantle heater 260 shown in FIGS. 1 and 10 isprovided so as to enclose the evacuating pipe 145. In addition, asillustrated in FIG. 10, the evacuating pipe 145 is divided into aplurality of portions, e.g., a first evacuating pipe 145 a and a secondevacuating pipe 145 b. The trap 258 and the second evacuating pipe 145 bare connected to the first evacuating pipe 145 a via a first connectingmember 266 and a second connecting member 268 respectively. In addition,the second evacuating pipe 145 b is connected to the process chamber 102shown in FIG. 1.

Also, as illustrated in FIG. 10, the mantle heater 260 enclosing thefirst evacuating pipe 145 a is divided into a plurality of portions,e.g., first˜third mantle heaters 260 a, 260 b and 260 c. The firstmantle heater 260 a is provided toward the second evacuating pipe 145 bwhich is heated by another mantle heater. The third mantle heater 260cis provided toward the trap 258. In addition, the second mantle heater260 b is provided between the first mantle heater 260a and the thirdmantle heater 260 c. The trap 258 is cooled. Thus, the portion of thefirst evacuating pipe 145 a corresponding to the position at which thesecond mantle heater 260 b is provided is cooled least readily, theportion of the first evacuating pipe 145 a at the position at which thefirst mantle heater 260 a is provided is cooled relatively readily andthe portion of the first evacuating pipe 145 a at the position at whichthe third mantle heater 260 c is provided is cooled most readily. Forthis reason, the temperature sensor 264 is mounted in the vicinity ofthe installation position at which the third mantle heater 260 c ismounted where the temperature of the evacuating pipe 145 can be detectedwith a high degree of sensitivity, e.g., at the first connecting member266.

The first˜third mantle heaters 260 a, 260 b and 260 c and thetemperature sensor 264 are connected to the heater controller 262. Thetemperature control device (not shown) of the heater controller 262calculates a target resistance by correcting the reference resistanceascertained in correspondence to the set temperature with a correctionvalue obtained based upon the temperature detected by the temperaturesensor 264. Then, first˜third heater control devices (not shown) of theheater controller 262 implement temperature control on the first˜thirdmantle heaters 260 a, 260 b and 260 c based upon the actual resistancesof the first third mantle heaters 260 a, 260 b and 260 c and the targetresistance. Other structural features are identical to those adopted inthe heater controller 160 explained earlier. In this structure, thereference resistance is corrected based upon the temperature detected bythe temperature sensor 264. As a result, even more accurate temperaturecontrol on the mantle heater 260 is achieved. It is to be noted thatthis embodiment may be adopted in the resistance heater 112 as well.

Fourth Embodiment

Next, the fourth embodiment of the present invention is explained. Thisembodiment is characterized in that the temperatures of a plurality ofheaters are controlled based upon the voltages applied to the individualheaters. The following is an explanation of the temperature controlimplemented on the first˜fourth cartridge heaters 146, 148, 150 and 152.

As shown in FIG. 11, a heater controller 400 is constituted of atemperature control device 402 and first˜fourth heater control devices404, 406, 408 and 410. The temperature control device 402 calculates areference voltage value in correspondence to the set temperature. Inaddition, the temperature control device 402 calculates a correctedreference voltage value by correcting the reference voltage value with acorrection value obtained in correspondence to the set temperature andthe temperature detected by the temperature sensor 250. Then, thetemperature control device 402 calculates target voltage values V_(s1),V_(s2), V_(s3) and V_(s4) by multiplying the corrected reference voltagevalue by temperature distribution constants K₁, K₂, K₃ and K₄. Otherstructural features are identical to those adopted in the temperaturecontrol device 164 explained earlier.

The first˜fourth heater control devices 404, 406, 408 and 410 arestructured identically to one another. In addition, the first˜fourthheater control devices 404, 406, 408 and 410 control the voltagesapplied to the first˜fourth cartridge heaters 146, 148, 150 and 152based upon the corresponding target voltage values V_(s1), V_(s2),V_(R3) and V_(R4) and feedback voltage values (actual voltage values)V_(R1), V_(R2) V_(R3) and V_(R4) of the first˜fourth cartridge heaters146, 148, 150 and 152, which are to be detailed later.

Now, an explanation is given on the first˜fourth heater control devices404, 406, 408 and 410 by focusing on the first heater control device 404as a typical example. The first heater control device 404 is constitutedof a heater control unit 412 and an interlock control unit 175. The 412is structured identically to the 174 shown in FIG. 6 except for that itis not provided with the current sensor 178, the low pass filter 182 andthe arithmetic unit 184. The first heater control device 404 assumingsuch a structure controls the phase of the AC power supplied to thefirst cartridge heater 146 based upon the target voltage value V_(s1)and the feedback voltage value V_(R1) of the first cartridge heater 146.

In other words, the feedback voltage value V_(R1) is input from thevoltage sensor 176 to the triac control unit 190 via the amplifier 186.The feedback voltage value V_(R1) is a value determined based upon thevalue of the voltage applied to the first cartridge heater 146. Inaddition, the target voltage value V_(s1) obtained at the temperaturecontrol device 402 is input to the triac control unit 190 via theamplifier 186. As illustrated in FIG. 7 referred to earlier, the triaccontrol unit 190 controls the phase of the AC power output from thetriac 192 to the first cartridge heater 146 so as to equalize thefeedback voltage value V_(R1) to the target voltage value V_(s1). It isto be noted that FIG. 12 illustrates the relationships among the changein the temperature of the first cartridge heater 146, the effectivevoltage value of the voltage applied to the first cartridge heater 146,the effective current value of the current flowing through the firstcartridge heater 146, the resistance at the first cartridge heater 146and the effective current value of the power supplied to the firstcartridge heater 146, achieved during the control operation in theembodiment. In addition, since the phase control implemented on the ACpower is identical to that in the first embodiment, its explanation isomitted.

In this structure, the feedback voltage value V_(R1) can be obtainedwithout having to perform an arithmetic operation and the power can bedirectly controlled in conformance to the feedback voltage value V_(R1).As a result, the temperature control on the first cartridge heater 146is facilitated. In addition, since it is not necessary to provide anarithmetic unit, the structure of the heater control unit 412 issimplified. It is to be noted that the embodiment may be also adopted inthe resistance heater 112 and in the mantle heaters 140, 144 and 260 aswell. Furthermore, while an example of the structure that phase controlis implemented on the power supplied to the first cartridge heater 146is explained in reference to the embodiment, the present invention isnot limited to this example, and the power may be controlled through,zero cross control or linear control to be explained later.

Fifth Embodiment

Next, the fifth embodiment of the present invention is explained. Thisembodiment is characterized in that zero cross control is implemented onthe power applied to the various heaters. Now, an explanation is givenin reference to the first heater control device 166 as a typicalexample. The first heater control device 166 in which the embodiment isadopted is provided with a zero cross control unit (not shown) insteadof the phase control unit 188. The zero cross control unit implementszero cross control on the AC power applied to the first cartridge heater146 so as to ensure that the heater resistance R_(R1) that has beeninput conforms to the target resistance R_(s1).

Namely, as illustrated in FIG. 13(a), the zero cross control unit setsthe number of power-ons higher than the number of power-offs, forexample, if the heater R_(R1) is lower than the target resistance R_(s1)and the temperature of the first cartridge heater 146 is lower than thetarget temperature. In addition, it sets the number of power-ons equalto the number of power-offs if, for instance, the heater resistanceR_(R1) is essentially equal to the target resistance R_(s1) and thetemperature of the first cartridge heater 146 is essentially equal tothe target temperature, as shown in FIG. 13(b). If the heater resistanceR_(R1) is higher than the target resistance R_(s1) and the temperatureof the first cartridge heater 146 is higher than the target temperature,it sets the number of power-ons smaller than the number of power-offs,for example, as shown in FIG. 13(c). Other structural features areidentical to those assumed in the CVD device 100. By adopting thisstructure, in which the power supplied to the first cartridge heater 146is turned on or off when the potential is at 0, noise in the power isless likely to occur. As a result, the stability in the temperature ofthe first cartridge heater 146 is improved.

Sixth Embodiment

Next, the sixth embodiment of the present invention is explained. Thisembodiment is characterized in that linear control (linear amplifiercontrol) is implemented on the power applied to the various heaters.Again, an explanation is given in reference to the embodiment byfocusing on the first heater control device 166 as a typical example.The first heater control device 166, in which the embodiment is adopted,is provided with a linear control unit (not shown) instead of the phasecontrol unit 188. The linear control unit continuously controls the ACpower applied to the first cartridge heater 146 so as to ensure that theheater resistance R_(R1) that has been input conforms to the targetresistance R_(s1).

Namely, as illustrated in FIG. 14(a), the linear control unitcontinuously increases the power if the heater resistance R_(R1) islower than the target resistance R_(s1) and the temperature of the firstcartridge heater 146 is lower than the target temperature. Also, itsustains the power at a specific level if the heater resistance R_(R1)is essentially equal to the target resistance R_(s1) and the temperatureof the first cartridge heater 146 is essentially equal to the targettemperature, as shown in FIG. 14(b). If the heater resistance R_(R1) ishigher than the target resistance R_(s1) and the temperature of thefirst cartridge heater 146 is higher than the target temperature, itdecreases the power continuously, as shown in FIG. 14(c). Otherstructural features are identical to those assumed in the CVD device100. By adopting this structure, in which the power applied to the firstcartridge heater 146 is adjusted on a continuous basis, noise is reducedto achieve an improvement in the temperature control.

Seventh Embodiment

The seventh embodiment of the present invention is now explained. Anexplanation is given above in reference to the first sixth embodimentson an example in which the temperatures at all locations including thewall of the process chamber 102 and the evacuating pipe 145 aresustained essentially at the same level. However, the present inventionis not restricted to such particulars, and may be adopted when thetemperatures at a plurality of specific positions of the object to beheated are to be sustained at different levels. The present inventionadopted in such an application is explained by focusing on thetemperature control implemented on the mantle heater 260 which heats theevacuating pipe 145 as explained earlier in reference to the thirdembodiment.

In the CVD device 100 shown in FIG. 1, the gas evacuated from theprocess chamber 102 is allowed to pass through the evacuating pipe 145in a gaseous state, and the gas which is then cooled in the trap 258 andbecomes liquefiable is collected. In addition, the gas which isevacuated as described above contains TiCl_(s4) and NH₃. The boilingpoint of TiCl₄ is 136.4° C., whereas the boiling point of NH₃ is−33.4°C. Thus, assuming that the evacuated gas contains only TiCl_(s4) andNH₃, the evacuating pipe 145 only needs to be heated to a temperatureequal to or higher than 136.4° C., i.e., the boiling point of TiCl₄. Thetemperature at the wall of the process chamber 102 is sustained at 150°C. Accordingly, in this embodiment, the temperature of the evacuatingpipe 145 toward the process chamber 102 is sustained at 150° C., forinstance, to ensure that the temperature at the wall of the processchamber 102 does not become lower, as in the embodiments explainedearlier. However, unlike in the previous embodiment, the temperature ofthe evacuating pipe 145 toward the trap 258 is sustained at 137° C., forinstance, so that TiCl₄ having a higher boiling point passes through theevacuating pipe 145 while remaining in a gaseous state to be promptlyliquefied inside the trap 258.

Accordingly, the set temperature for the temperature control device (notshown) of the heater controller 262 is first selected at, for instance,137° C. The temperature control device then obtains a referenceresistance in correspondence to the set temperature. In addition, thetemperature control device corrects the reference resistance by using acorrection value obtained based upon the temperature detected by thetemperature sensor 264 as necessary to obtain a corrected referenceresistance. The process explained thus far is identical to that in theprevious embodiments.

In addition, the temperature control device calculates targetresistances R_(s1), R_(s2) and R_(s3) by multiplying the correctedreference resistance by temperature distribution constants K₁, K₂ and K₃that determine the temperature distribution at the positions at whichheat is applied by the first third mantle heaters 260 a, 260 b and 260 cshown in FIG. 10 as explained earlier. However, in this embodiment, thetemperature at the position where heat is applied by the first mantleheater 260 a is sustained at 150° C. The temperature at the positionwhere heat is applied by the third mantle heater 260 c is sustained at137° C. The temperature at the position where heat is applied by thesecond mantle heater 260 b is sustained at a level within the range of137° C. 150° C., e.g., 144° C. For this reason, the temperaturedistribution constants K₁, K₂ and K₃ are set at values which will createthe temperature gradient described above at the individual positions ofthe evacuating pipe 145 a in correspondence to a single set temperatureat the temperature control device.

Namely, the temperature distribution constants K₁, K₂ and K₃ aredetermined as described below. First, a temperature sensor is providedat each of the positions at which heat is applied by the first thirdmantle heaters 260 a, 260 b and 260 c. Next, the temperatures of thefirst third mantle heaters 260 a, 260 b and 260 c are controlledindependently of one another, by the first third heater control devices(not shown) of the heater controller 262. Through this control, heat isapplied at the different positions by the first˜third mantle heaters 260a, 260 b and 260 c to sustain the temperatures at the different levelsexplained earlier. During this process, the temperatures at thedifferent positions are monitored by the corresponding temperaturesensors. When the temperatures at the various positions have becomestabilized, the actual resistances at the first˜third mantle heaters 260a, 260 b and 260 c are recorded.

Next, the temperature distribution constants K₁, K₂ and K₃ areascertained in correspondence to the actual resistances that have beenrecorded. First, 1 is set for the temperature distribution constant K₃at the position where the evacuating pipe 145 a is heated by the thirdmantle heater 260 c to the lowest level, for instance. This heatapplication position is also the position at which the temperature hasbeen detected by the temperature sensor 264. In addition, thetemperature distribution constant K₁ corresponding to the position atwhich heat is applied by the first mantle heater 260 a and thetemperature distribution constant K₂ corresponding to the position atwhich heat is applied by the second mantle heater 260 b are calculatedso that different temperature distributions are achieved at theindividual heat application positions as explained earlier, relative tothe heat distribution constant K₃. At the heat application positionscorresponding to the temperature distribution constants K₁ and K₂, thetemperatures have been detected by the corresponding temperature sensorsother than the temperature sensor 264. As a result, the temperaturedistribution constants K₁, K₂ and K₃ achieve a relationship expressedas;

K ₁ >K ₂ >K ₃.

To explain the control achieved by the heater controller 262 in furtherdetail, the temperature control device multiplies the correctedreference resistance by the temperature distribution constants K₁, K₂and K₃ and obtains target resistance values R_(s1), R_(s2) and R₃. Then,the first third heater control devices implement temperature control onthe first third mantle heaters 260 a, 260 b and 260 c based upon theactual resistances at the first third mantle heaters 260 a, 260 b and260 c and the target resistances. Other structural features areidentical to those assumed in the heater controller 160 explainedearlier. By using the target resistances R_(s1), R_(s2) and R_(s3) inthe temperature control described above, the temperatures at theindividual heat application positions can be sustained at differentlevels in correspondence to a single set temperature. Thus, it is notnecessary to set different temperatures at the temperature controldevice for the individual heat application positions at which heat isapplied by the first˜third mantle heaters 260 a, 260 b and 260 c. It isto be noted that the embodiment may be adopted in temperature control onthe resistance heater 112, the mantle heaters 140 and 144, thefirst˜fourth cartridge heaters 146, 148, 150 and 152 and other heaters,as well. In addition, the embodiment may be adopted in the voltagecontrol explained earlier in reference to the fourth embodiment, aswell.

While the invention has been particularly shown and described withrespect to preferred embodiments thereof by referring to the attacheddrawings, the present invention is not limited to these examples and itwill be understood by those skilled in the art that various changes inform and detail may be made therein without departing from the spirit,scope and teaching of the invention.

For instance, while an explanation is given above in reference to theembodiments on an example in which the heating elements of the heatersare constituted of an Fe-Ni alloy, the present invention is notrestricted to these particulars and it may be adopted in conjunctionwith heating elements constituted of any of various materials whoseresistances change greatly in correspondence to the temperature.

In addition, while an explanation is given above in reference to theembodiments on an example in which the power to each heater iscontrolled so as to ensure that the heater resistance conforms to thetarget resistance even when the temperature of the member to be heatedhas not yet reached the set temperature immediately after startup or thelike of the apparatus, the present invention is not restricted to thesedetails. The present invention may be adopted when rapidly heating themember to be heated to the set temperature by supplying excessive powerto the individual heaters. Even in such a case, since a resister whoseresistance increases as the temperature rises to result in a reductionin the current value is employed in each heater, no damage occurs.

Furthermore, while an explanation is given above in reference to theembodiments on an example in which heaters and heater controllers thatmay adopt the present invention are utilized to heat various membersconstituting a thermal CVD device and various members connected to thethermal CVD device, the present invention is not restricted to theseparticulars, and it may be adopted in various types of semiconductormanufacturing apparatuses including plasma processing apparatuses suchas a plasma CVD apparatus, a plasma etching apparatus and a plasmaashing apparatus and in various apparatuses and members that need to beheated.

According to the present invention, temperature control is implementedon a plurality of means for heating based upon the resistances at theindividual means for heating or the voltages applied to the individualmeans for heating. Thus, the need for providing a means for temperaturedetection, a means for overheat detection or the like for each means forheating is eliminated. Furthermore, since the number of wirings to beconnected to the individual means for temperature detection is alsoreduced, the structure of the apparatus is simplified. Thus, the initialcost is minimized, the maintenance work on the means for heating and thetemperature controllers is facilitated and miniaturization of theapparatus is achieved. Moreover, the temperatures of the means forheating are directly measured according to the present invention. Thetemperature control on all the means for heating is implemented as awhole based upon the temperatures detected by the means for temperaturedetection. Consequently, a higher degree of accuracy is achieved in thetemperature management. In addition, even when a single member is heatedwith a plurality of means for heating, temperature control isimplemented on the individual means for heating as a whole. As a result,the individual means for heating do not interfere with one another, toachieve even heating.

INDUSTRIAL APPLICABILITY

The present invention may be adopted in various types of semiconductormanufacturing apparatuses including a thermal CVD device and plasmaprocessing apparatuses such as a plasma CVD devices, a plasma etchingapparatus and a plasma ashing apparatus, and also in the variousapparatuses and members that need to be heated.

Explanation of Reference Numerals

100 CVD device

102 process chamber

106 stage

108 gas outlet member

110, 138, 142, 160, 262 heater controller

112 resistance heater

140, 144, 260 mantle heater

146, 148, 150, 152 first˜fourth cartridge heaters

156 heating wire

164 temperature control device

166, 168, 170,172 first˜fourth heater control devices

174 heater control unit

175 interlock control unit

176 voltage sensor

178 current sensor

184 arithmetic unit

190 phase control unit

250 temperature sensor

W wafer

What is claimed is:
 1. A temperature control apparatus for implementingtemperature control on a means for heating that heats an object to beheated, comprising; at least two means for heating each with aresistance that increases as the temperature rises; at least one meansfor temperature detection that detects the temperature of the object tobe heated; a means for target resistance calculation that calculates atarget resistance for each of said means for heating by correcting areference resistance determined based upon a set temperature for theobject to be heated with a correction value obtained in correspondenceto the temperature detected by said means for temperature detection andmultiplying the corrected reference resistance by a temperaturedistribution constant that is determined in advance for each of saidmeans for heating to adjust the temperature distribution at the objectto be heated; a means for actual resistance calculation that calculatesan actual resistance at each of said means for heating based upon afeedback voltage value obtained based upon the voltage applied to saidmeans for heating and a feedback current value obtained based upon thecurrent flowing through said means for heating; and a means for powercontrol that controls the power applied to each of said means forheating so that the actual resistance at said means for heating conformsto the target resistance.
 2. A temperature control apparatus forimplementing temperature control on a means for heating according toclaim 1, wherein; said means for power control is a means for phasecontrol that implements phase control on the power applied to each ofsaid means for heating.
 3. A temperature control apparatus forimplementing temperature control on a means for heating according toclaim 2, wherein; said means for phase control increases the length oftime over which power is applied if the actual resistance is lower thanthe target resistance; said means for phase control sustains the currentlength of time over which power is applied if the actual resistance isequal to the target resistance; and said means for phase control reducesthe length of time over which power is applied if the actual resistanceis higher than the target resistance.
 4. A temperature control apparatusfor implementing temperature control on a means for heating according toclaim 1, wherein; said means for power control is a means for zero crosscontrol that implements zero cross control on the power applied to eachof said means for heating.
 5. A temperature control apparatus forimplementing temperature control on a means for heating according toclaim 1, wherein; said means for power control is a means for linearcontrol that implements linear control on the power applied to each ofsaid means for heating.
 6. A temperature control apparatus forimplementing temperature control on a means for heating according toclaim 1, wherein; a means for power supply suspension that suspendspower supply to said means for heating if the actual resistance becomeshigher than a resistance upper limit or becomes lower than a resistancelower limit.
 7. A temperature control apparatus for implementingtemperature control on a means for heating according to claim 1,wherein; the object to be heated is a member constituting saidsemiconductor manufacturing apparatus and the like.
 8. A temperaturecontrol apparatus for implementing temperature control on a means forheating that heats an object to be heated, comprising; at least twomeans for heating each with a resistance value increasing as thetemperature rises; at least one means for temperature detection thatdetects the temperature of the object to be heated; a means for targetvoltage calculation that calculates a target voltage for each of saidmeans for heating by correcting a reference voltage determined basedupon the set temperature for the object to be heated with a correctionvalue obtained in correspondence to the temperature detected by saidmeans for temperature detection and multiplying the corrected referencevoltage by a temperature distribution constant that is determined inadvance for each of said means for heating to adjust the temperaturedistribution at the object to be heated; a means for voltage detectionthat detects an actual voltage applied to each of said means forheating; and a means for power control that controls the power appliedto each of said means for heating so that the actual voltage at saidmeans for heating conforms to the target voltage.
 9. A temperaturecontrol apparatus for implementing temperature control on a means forheating according to claim 8, wherein; said means for power control is ameans for phase control that implements phase control on the powerapplied to each of said means for heating.
 10. A temperature controlapparatus for implementing temperature control on a means for heatingaccording to claim 9, wherein; said means for phase control increasesthe length of time over which power is applied if the actual voltage islower than the target voltage; said means for phase control sustains thecurrent length of power application if the actual voltage is essentiallyequal to the target voltage; and said means for phase control reducesthe length of time over which power is applied if the actual voltage ishigher than the target voltage.
 11. A temperature control apparatus forimplementing temperature control on a means for heating according toclaim 8, wherein; said means for power control is a means for zero crosscontrol that implements zero cross control on the power applied to eachof said means for heating.
 12. A temperature control apparatus forimplementing temperature control on a means for heating according toclaim 8, wherein; said means for power control is a means for linearcontrol that implements linear control on the power applied to each ofsaid means for heating.
 13. A temperature control apparatus forimplementing temperature control on a means for heating according toclaim 8, wherein; a means for power supply suspension that suspends thepower supply to said means for heating if the actual voltage becomeshigher than a voltage upper limit or becomes lower than a voltage lowerlimit.
 14. A temperature control apparatus for implementing temperaturecontrol on a means for heating according to claim 8, wherein; the objectto be heated is a member constituting said semiconductor manufacturingapparatus and the like.
 15. A temperature control method forimplementing temperature control on a means for heating that heats anobject to be heated, comprising; a step in which a reference resistancedetermined based upon the set temperature for the object to be heated iscorrected by using a correction value obtained in correspondence to thetemperature of the object to be heated detected by, at least, one meansfor temperature detection; a step in which the corrected referenceresistance is multiplied by a temperature distribution constant used toadjust the temperature distribution at the object to be heated, which isdetermined in advance for each of at least two means for heating eachwith a resistance that increases in correspondence to a temperatureincrease to obtain a target resistance for each of said means forheating; a step in which the actual resistance at each of said means forheating is ascertained based upon a feedback voltage which correspondsto the voltage applied to said means for heating and a feedback currentwhich corresponds to the current flowing through said means for heating;and a step in which the power applied to each of said means for heatingis controlled so that the actual resistance at said means for heatingconforms to the target resistance.
 16. A temperature control method forimplementing temperature control on a means for heating according toclaim 15, wherein; in said step for power control, phase control isimplemented on the power applied to each of said means for heating. 17.A temperature control method for implementing temperature control on ameans for heating according to claim 16, wherein; said step forimplementing phase control includes; a step in which the length of timeover which power is applied is increased if the actual resistance islower than the target resistance; a step in which the current length ofpower application time is sustained if the actual resistance isessentially equal to the target resistance; and a step in which thelength of time over which power is applied is reduced if the actualresistance is higher than the target resistance.
 18. A temperaturecontrol method for implementing temperature control on a means forheating according to claim 15, wherein; in said step for power control,zero cross control is implemented on the power applied to each of saidmeans for heating.
 19. A temperature control method for implementingtemperature control on a means for heating according to claim 15,wherein; in said step for power control, linear control is implementedon the power applied to each of said means for heating.
 20. Atemperature control method for implementing temperature control on ameans for heating according to claim 15, further comprising; a step inwhich power supply to said means for heating is suspended if the actualresistance becomes higher than a resistance upper limit or the actualresistance becomes lower than a resistance lower limit.
 21. Atemperature control method for implementing temperature control on ameans for heating according to claim 15, wherein; the object to beheated is a member constituting said semiconductor manufacturingapparatus and the like.
 22. A temperature control method forimplementing temperature control on a means for heating that heats anobject to be heated, comprising; a step in which a reference voltagedetermined based upon the set temperature for the object to be heated iscorrected by using a correction value obtained in correspondence to thetemperature of the object to be heated detected by, at least, one meansfor temperature detection; a step in which the corrected referencevoltage is multiplied by a temperature distribution constant used toadjust the temperature distribution at the object to be heated, which isdetermined in advance for each of at least two means for heating eachwith a resistance that increases in correspondence to a temperatureincrease to obtain a target voltage for each of said means for heating;a step in which the actual voltage applied to each of said means forheating is detected; and a step in which the power applied to each ofsaid means for heating is controlled so that the actual voltage at saidmeans for heating conforms to the target voltage.
 23. A temperaturecontrol method for implementing temperature control on a means forheating according to claim 23, wherein; in said step for power control,phase control is implemented on the power applied to each of said meansfor heating.
 24. A temperature control method for implementingtemperature control on a means for heating according to claim 23,wherein; said step for implementing phase control includes; a step inwhich the length of time over which power is applied is increased if theactual voltage is lower than the target voltage; a step in which thecurrent length of power application time is sustained if the actualvoltage is essentially equal to the target voltage; and a step in whichthe length of time over which power is applied is reduced if the actualvoltage is higher than the target voltage.
 25. A temperature controlmethod for implementing temperature control on a means for heatingaccording to claim 22, wherein; in said step for power control, zerocross control is implemented on the power applied to each of said meansfor heating.
 26. A temperature control method for implementingtemperature control on a means for heating according to claim 22,wherein; in said step for power control, linear control is implementedon the power applied to each of said means for heating.
 27. Atemperature control method for implementing temperature control on ameans for heating according to claim 22, further comprising; a step inwhich power supply to said means for heating is suspended if the actualvoltage becomes higher than a voltage upper limit or the actual voltagebecomes lower than a voltage lower limit.
 28. A temperature controlmethod for implementing temperature control on a means for heatingaccording to claim 22, wherein; the object to be heated is a memberconstituting said semiconductor manufacturing apparatus and the like.